The study plans to relate the molecular composition of the red-green color vision gene complex as studied by an analysis of DNA from blood specimens to assessment of color vision by various noninvasive psychophysical measurements. Various red-green color vision defects are found in 8% of Caucasian male individuals. Such defects are caused by rearrangements and deletions of the red green pigment genes that are located very close to each other on the X chromosome. Considerable complexity in these molecular patterns has been found. Different molecular patterns can be associated with a given color vision anomaly and complex pigment gene patterns have been found in individuals with normal color vision. In this study the detailed molecular makeup of color vision genes will be determined in populations of differing ancestry (Caucasian, Afro-American, Japanese, and others) as well as in Old World monkeys. Particular attention will be given to the exact molecular definition of fusion genes that are composed of segments of both red and green pigment gene material and their effect on color vision phenotypes. Phenotypic studies will be done in humans to correlate the genetic-molecular findings with refined psychophysical measurement of vision anomalies and defects. A hypothesis will be tested that predicts a lower frequency of color vision defects in populations where individuals with normal color vision have fewer green pigment genes than are observed in the Caucasian population where color normal individuals with two or more green genes are common. On a practical plane, the in vitro study of color vision provides genetic markers for a variety of investigations and may lead to blood tests for the diagnosis of color vision defects. The elucidation of the molecular- genetic structure of this complex locus affecting sensory perception correlated to its phenotypic effects provides a model for future study of complex human genes on phenotypes affecting perception and behavior.
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